Soap bars for cleansing are typically prepared by saponification/neutralizing triglyceride/fatty acids. In this saponification process, various fats (e.g., tallow, palms and coconut oil blends) are saponified in the presence of alkali (typically NaOH) to yield alkaline salts of fatty acid (derived from the fatty acid chains forming the glyceride) and glycerol. Glycerol is then typically extracted with brine to yield dilute fatty acid soap solution containing soap and aqueous phase (e.g., 70% soap and 30% aqueous phase). The soap solution is then typically dried (e.g., to about 12% water) and the remaining mass is milled, plodded and stamped into bars. Alternatively, the soap solution can be cast in to moulds, blisters etc.
The chain length of fatty acid soaps varies depending on starting fat or oil feedstock (for purposes of this specification, “oil” and “fat” as used interchangeably, except where context demands otherwise). Longer chain fatty acid soaps (e.g., C16 palmitic or C18 stearic) are typically obtained from tallow and palm oils, and shorter chain soaps (e.g., C12 lauric) may typically be obtained from, for example, coconut oil or palm kernel oil. The fatty acid soaps produced may also be saturated or unsaturated (e.g., oleic acid).
Typically, longer molecular weight fatty acid soaps (e.g. C14 to C22 soaps) are insoluble and do not generate foam, despite the fact that they can help making the foam generated by other soluble soaps creamier and more stable. Conversely, shorter molecular weight soaps (e.g., C8 to C17) lather quickly. However, the longer chain soaps are desirable in that they maintain structure and do not dissolve as readily. Unsaturated soaps (e.g., oleic) are soluble and lather quickly, like short-chained soaps, but form a denser, creamier foam, like the longer chained soaps.
Generally, particularly because of the structuring required to produce and maintain a solid soap bar (i.e. structuring is provided by longer chain-length soaps) the production of a pure soap bar having enhanced lathering benefit (e.g., quick lather) is considered extremely difficult.
When synthetic surfactant (e.g., nonionic surfactant) is added to enhance mildness, typically the soap bar must still be predominantly made of long-chain soaps to ensure the bar is well structured and can maintain structure in stamping.
WO 93/04161 (P&G), for example, discloses bars comprising mixtures of soap, C14-C20 alkyl polyethoxylate nonionic and C16-C18 acyl isethionate (also a mild surfactant). The soap used comprises at least tallow (longer chain, slower lather) and includes cationic polymeric skin mildness aids and, as moisturizers, free fatty acid.
To overcome poor lathering problems, references in the art have disclosed use of specially tailored soaps (which involved additional, expensive processing) and/or use of additional, expensive co-actives.
U.S. Pat. No. 5,540,852, Kefauver et al., for example, discloses a mild, lathering personal cleansing soap bar composition comprising from 30 to 85 by wt. tailored fatty acid soap comprising in turn from 50% to 85% of saturated fatty acid soap selected from the group consisting of: myristic, palmitic, and stearic acid soaps. Kefauver fails to disclose that minimum levels of capric and lauric fatty acid soaps and maximum levels of myristic fatty acid are required for enhanced lather.
U.S. Pat. No. 5,656,579, Chambers et al. discloses a mild toilet soap bar comprising blends of soap with one or more coactives, comprising at least 25% wt. on total actives of lauric acid soaps. Again, Chambers fails to disclose soap bar formulations having low amounts of myristic acid soap, or having levels of capric and lauric fatty acid soaps as claimed in our invention.
Thus, previous attempts for enhance mildness and/or in-use performance are provided by specialized tailoring or use of expensive co-actives.
Nowhere is there disclosed compositions providing enhanced lather while retaining structure using simple, but unexpected, ratios of soap as provided by applicants' claimed invention.
The present invention is the result of experimentation investigating the use of different fatty acids in varying amounts as an alternative to synthetic surfactants to improve lathering properties while maintaining structuring properties. Surprisingly, soap bars with superior lathering which retained structuring properties can be obtained.
The compositions of the present invention have shown to yield bars with substantially improved lather volume performance in respect to total volume.